1. Technical Field
The present invention relates to a pressure regulating mechanism that is used in a liquid ejecting apparatus. More specifically, the present invention relates to a pressure regulating mechanism that has a pressure receiving member which is capable of deforming inside a pressure regulating chamber when the pressure in the pressure regulating chamber is reduced to be less than a predetermined pressure.
2. Related Art
Liquid ejecting apparatuses currently known in the art have liquid ejecting heads that are capable of discharging various kinds of liquids. One type of liquid ejecting apparatus is an image recording apparatus that discharges ink droplets onto a recording medium, such as paper, during a recording process. In addition, liquid ejecting apparatuses have been used in various manufacturing apparatuses, such as liquid crystal displays, plasma displays, organic EL (Electro Luminescence) displays, or FEDs (Field Emission Displays). Such liquid ejecting apparatuses are used to discharge various liquid materials, such as color materials or electrode materials, onto image forming regions or electrode forming regions.
In an “off-carriage” type of liquid ejecting apparatus, such as the apparatus described in Japanese Patent Application No. JP-A-2005-186344, a liquid supply source (ink cartridge) is disposed in an apparatus main body, and a pressure regulating mechanism is used to supply ink from a liquid supply source to the liquid ejecting head. The pressure regulating mechanism regulates the pressure of the ink to a predetermined pressure. The liquid supply source and the pressure regulating mechanism are connected with each other by a flexible liquid supply tube.
The pressure regulating mechanism includes a pressure regulating chamber stores a liquid and has an inlet port and an outlet port, an on/off valve that opens and closes the inlet port, a biasing member that biases the on/off valve toward the inlet port, a film member that is stretched to seal an opening surface of the pressure regulating chamber, and an actuating lever adhered to the film member. In this configuration, if an internal pressure of the pressure regulating chamber is reduced to less than a predetermined pressure, the film member is elastically deformed inside the pressure regulating chamber, and the actuating lever presses the on/off valve to an open position by an actuating force obtained when the film member is elastically deformed, and ink flows into the pressure chamber through the inlet port.
Ideally, the ink flow passage from the ink cartridge to nozzle openings of a recording head is filled with ink. However, in the configuration described above, it is often difficult to completely prevent air bubbles from entering the ink flow passage. Particularly, in configurations where a pressure regulating mechanism is used, external gas (air) may pass through the film member and mix with ink in the pressure regulating chamber, resulting in the formation of air bubbles. Unfortunately, however, if the air bubbles are able to move toward the recording head, the change in the ink pressure created during the discharge operation may be absorbed by the air bubbles, resulting in pressure loss. In addition, the air bubbles may block the flow passage, which may create difficulties adequately supplying the ink to the recording head.